Ignite - To heat a gaseous mixture to the temperature at which combustion takes place.
Ignition Point - The minimum temperature at which combustion of a solid or fluid can occur.
Illuminance - A measure of the amount of light incident on a surface; measured in foot-candles or Lux.
Impulse Turbine - A turbine that is driven by high velocity jets of water or steam from a nozzle directed to vanes or buckets attached to a wheel. (A pelton wheel is an impulse hydroturbine).
Incandescent - These lights use an electrically heated filament to produce light in a vacuum or inert gas-filled bulb.
Incident Solar Radiation - The amount of solar radiation striking a surface per unit of time and area.
Independent Power Producer - A company or individual that is not directly regulated as a utility. These entities produce power for their own use and/or sell it to regulated utilities.
Indirect Solar Gain System - A passive solar heating system in which the sun warms a heat storage element, and the heat is distributed to the interior space by convection, conduction, and radiation.
Indirect Water Heater - A type of water heater that circulates water through a heat exchanger in a boiler. The heated water then flows into an insulated storage tank.
Induction - The production of an electric current in a conductor by the variation of a magnetic field in its vicinity.
Induction Generator - A device that converts the mechanical energy of rotation into electricity based on electromagnetic induction. An electric voltage (electromotive force) is induced in a conducting loop (or coil) when there is a change in the number of magnetic field lines (or magnetic flux) passing through the loop. When the loop is closed by connecting the ends through an external load, the induced voltage will cause an electric current to flow through the loop and load. Thus rotational energy is converted into electrical energy.
Induction Motor - A motor in which a three phase (or any multiphase) alternating current (i.e. the working current) is supplied to iron-cored coils (or windings) within the stator. As a result, a rotating magnetic field is set up, which induces a magnetizing current in the rotor coils (or windings). Interaction of the magnetic field produced in this manner with the rotating field causes rotational motion to occur.
Industrial Process Heat - The thermal energy used in an industrial process.
Inert Gas - A gas that does not react with other substances; e.g. argon or krypton; sealed between two sheets of glazing to decrease the U-value (increase the R-Value) of windows.
Infrared Radiation - Electromagnetic radiation whose wavelengths lie in the range from 0.75 micrometer to 1000 micrometers; invisible long wavelength radiation (heat) capable of producing a thermal or photovoltaic effect, though less effective than visible light.
Insolation - The solar power density incident on a surface of stated area and orientation, usually expressed as Watts per square meter or Btu per square foot per hour.
Installed Capacity - The total capacity of electrical generation devices in a power station or system.
Instantaneous Efficiency (of a Solar Collector) - The amount of energy absorbed (or converted) by a solar collector (or photovoltaic cell or module) over a 15 minute period.
Insulation - Materials that prevent or slow down the movement of heat.
Insulation Blanket - A pre-cut layer of insulation applied around a water heater storage tank to reduce standby heat loss from the tank.
Insulator - A device or material with a high resistance to electricity flow.
Integrated Collector/Storage (ICS) Solar Systems - ICS solar systems are also called "batch" or "breadbox" water heaters. They combine the collector and storage tank in one unit. The sun shining into the collector strikes the storage tank directly, heating the water. The large thermal mass of the water, plus methods to reduce heat loss through the tank, prevent the stored water from freezing.
Integrated Heating Systems - A type of heating appliance that performs more than one function, for example space and water heating.
Integrated Resource Plan (IRP) - A plan developed by an electric utility, sometimes as required by a public regulatory commission or agency, that defines the short and long term capacity additions (supply side) and demand side management programs that it will undertake to meet projected energy demands.
Interconnection - A connection or link between power systems that enables them to draw on each other's reserve capacity in time of need.
Intermittent Generators - Power plants, whose output depends on a factor(s) that cannot be controlled by the power generator because they utilize intermittent resources such as solar energy or the wind.
Internal Combustion Electric Power Plant - The generation of electric power by a heat engine which converts part of the heat generated by combustion of the fuel into mechanical motion to operate an electric generator.
Internal Gain - The heat produced by sources of heat in a building (occupants, appliances, lighting, etc).
Internal Mass - Materials with high thermal energy storage capacity contained in or part of a building's walls, floors, or freestanding elements.
Internal Rate of Return - A widely used rate of return for performing economic analysis. This method solves for the interest rate that equates the equivalent worth of an alternative's cash receipts or savings to the equivalent worth of cash expenditures, including investments. The resultant interest rate is termed the internal rate of return (IRR).
Interruptable Load - Energy loads that can be shut off or disconnected at the supplier's discretion or as determined by a contractual agreement between the supplier and the customer.
Intrinsic Layer - A layer of semiconductor material (as used in a solar photovoltaic device) whose properties are essentially those of the pure, undoped, material.
Inverter - A device that that converts direct current electricity (from for example a solar photovoltaic module or array) to alternating current for use directly to operate appliances or to supply power to a electricity grid.
Investment Tax Credit - A tax credit granted for specific types of investments.
Investor Owned Utility (IOU) - A utility owned by stockholders or other investors; sometimes referred to as a private utility, in contrast to a public utility that is owned by a government agency or cooperative.
Ion - An electrically charged atom or group of atoms that has lost or gained electrons; a loss makes the resulting particle positively charged; a gain makes the particle negatively charged.
Ionizer - A device that removes airborne particles from breathable air. Negative ions are produced and give up their negative charge to the particles. These new negative particles are then attracted to the positive particles surrounding them. This accumulation process continues until the particles become heavy enough to fall to the ground.
Irradiance - The direct, diffuse, and reflected solar radiation that strikes a surface.
Isolated Solar Gain System - A type of passive solar heating system where heat is collected in one area for use in another.
I-Type Semiconductor - A semiconductor material that is left intrinsic, or undoped so that the concentration of charge carriers is characteristic of the material itself rather than of added impurities.
I-V Curve - A graphical plot or representation the current and voltage output of a solar photovoltaic cell or module as a load on the device is increased from short circuit (no load) condition to the open circuit condition; used to characterize cell/module performance.
Electro Industries, Inc., 2150 West River Street, PO Box 538,
Monticello, MN 55362 (Map)
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